1. Field of the Invention
The present invention relates to monolithic ceramic capacitors and is directed more particularly to low value monolithic capacitors, particularly adapted for use in high frequency circuits i.e. circuits operating in frequencies of from a megahertz and beyond.
The invention is further directed to capacitors of the type described having relatively low values in the range of up to about 25 to 30 pico farads.
2. The Prior Art
Conventional ceramic capacitors of the monolithic type are typically comprised of two or more electrode layers encapsulated within a monolith of fired ceramic dielectric material. Typical monolithic ceramic capacitors and methods of making the same are illustrated in the following U.S. Pat. Nos. Re. 26,421 reissued July 2, 1968 and 3,456,313 issued July 22, 1969.
In capacitors of the type described, it is conventional to fabricate the electrode layers in such manner that a layer or layers of the same polarity include marginal edges exposed at one side of the monolith. An electrode layer or layers of opposite polarity include margin portions exposed at an opposite side of the monolith. The edges of the electrodes remote from the exposed margins terminate short of the opposite surface of the monolith with the result that electrodes of opposite polarity overlap for a major portion of their surface areas. Capacitors of the type described are terminated by applying a conductive coating over each of the edges of the monolith at which the margins of the electrodes are exposed.
Multilayer capacitors of the type described hereinabove are highly efficient and compact, providing substantial capacitance in a small package. Where low capacitance values are required resort has been had to monolithic capacitors having only two electrode layers within the ceramic matrix, the layers being separated by a dielectric layer. The use of a single electrode of each polarity is necessitated by the fact that if multiple layers were employed the dimensions of the capacitor would be so small as to render the manufacture and subsequent handling of the capacitor impracticable.
While two electrode monolithic ceramic capacitors of the type described are effectively used in many applications, attempts to employ such capacitors in high frequency circuitry have demonstrated that the dissipation factor (DF) of such capacitors, their low efficiency and their high equivalent series resistance (ESR) have militated against the use of monolithic ceramic capacitors in low value, high frequency applications.